Imaging system and methodology employing reciprocal space optical design

ABSTRACT

An imaging system and methodology is provided to facilitate optical imaging performance. The system includes a sensor having one or more receptors and an image transfer medium to scale the sensor and receptors to an object field of view. A computer, memory, and/or display associated with the sensor provides storage and/or display of information relating to output from the receptors to produce and/or process an image, wherein a plurality of illumination sources can also be utilized in conjunction with the image transfer medium. The image transfer medium can be configured as a k-space filter that correlates a pitch associated with the receptors to a diffraction-limited spot within the object field of view, wherein the pitch can be unit-mapped to about the size of the diffraction-limited spot within the object field of view.

PRIORITY CLAIM

[0001] This application is a continuation application of Ser. No.10/403,744, filed on Mar. 31, 2003, and entitled IMAGING SYSTEM ANDMETHODOLOGY EMPLOYING RECIPROCAL SPACE OPTICAL DESIGN, which is acontinuation application of U.S. Ser. No. 09/900,218, filed on Jul. 6,2001, and entitled IMAGING SYSTEM AND METHODOLOGY EMPLOYING RECIPROCALSPACE OPTICAL DESIGN, and now issued as U.S. Pat. No. 6,664,528. Theserelated applications are incorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention relates generally to image and opticalsystems, and more particularly to a system and method to facilitateimaging performance via an image transfer medium that projectscharacteristics of a sensor to an object field of view.

BACKGROUND OF THE INVENTION

[0003] Optical technologies and sciences related to such fields asmicroscopy have evolved from ancient observations and understandings ofthe nature of light to the manner in which light can be manipulated viaone or more optical devices such as through a lens. In fact, somesources have cited that Zacharias Jansen—of Holland in 1595, waspossibly the first inventor of a multiple lens or compound microscopedesign. After Jansen, many improvements were incorporated intomicroscope designs over the centuries leading up to Lord Rayleigh's andErnst Abbe's discoveries in the 19th century regarding diffractionlimitations in lenses. These scientists demonstrated that physical lawsof diffraction require that a minimum resolving distance of a lens isrelated to the wavelength of light divided by a parameter referred to asthe Numeric Aperture of the lens. By the 1880's, oil immersion objectivelenses were developed having a Numeric Aperture of about 1.4—leading theway for light microscopes to resolve between two small points at aboutthe theoretical diffraction limits established by Rayleigh and Abbe. Theresolution demonstrated by lenses operating at the limits of diffractiontheory, however, is rarely achieved in practice without sacrificingother desirable characteristics. For instance, as light microscopedesigns continued to develop in the 20th century, increasedmagnification of smaller and smaller objects also continued, wherebymany of the best microscope designs can offer visually “pleasing images”at about 1000 times magnification. Unfortunately, increasedmagnification in conventional microscope designs generally causestradeoffs in other design features such as resolution and contrast.

[0004] In order to illustrate these tradeoffs, the following discussionprovides a conventional microscope design methodology that has developedover the ages. Conventional microscope designs limit usefulmagnifications to approximately 1000 times (×) since the intrinsicspatial resolution of the lenses cannot exceed limits dictated by thewell-known Rayleigh equation:

R=1.22λ/(NA _(OBJECT) +NA _(CONDENSER))

[0005] Thus, for a conventional 100× high resolution,“Infinity-Corrected”, oil immersion objective lens, having a standardmaximum Numerical Aperture of 1.25, utilized in conjunction with aregularly employed setting for the highest contrast of a sub-stage,in-air lighting condenser, having a Numerical Aperture of 0.9 employedin conjunction with oil-immersion condensers having a Numerical Apertureof up to 1.4 (e.g., modern Kohler Lighting configurations), and appliedat a standard illumination wavelength of 0.55 micron, for example, theresulting known best theoretical spatial resolution at the highestuseful magnification is therefore about 0.312 microns (312 nanometers).Any increase in magnification increases image size but also results inwell-known increased detail blur at the image plane. Consequently,typical best visual spatial resolution is based on contrast andmagnification of so-called “pleasing images” and rarely actually exceeds500 nanometers (0.5 microns) and is regularly on the order of 1000nanometers (1 micron).

[0006] In modem times, optical designs have been applied to othertechnologies such as digital imaging, machine vision for direct imaging,inspection, fiducial and absolute measurement, counting, characterizinggeometry, morphology, coordinate location, spectral information,analytical imaging for identification, medical clinical microscopicimaging, and a plurality of other image-based applications. In addition,video imaging techniques and associated computerized image processingmethods have long been a standard inspection technique in manyindustries and applications. High resolution and high magnificationvideo-based imaging systems have conventionally relied upon knowntechniques of conventional microscopic instrumentation coupled to avideo camera or other device. Other variations have typically employedwell-known “macro” and “tele-zoom” optical lens components, (long rangeand short range) coupled to video camera devices to achieve highmagnification as well. Though many of the imaging applications mentionedabove, employ these techniques regularly, the methods have been subjectto optical and illumination related limitations that can causesubstantial degradation of image quality and usefulness when highmagnification and resolution are required.

[0007] Well-defined and known limitations of conventionalhigh-magnification and/or high-resolution imaging systems include butare not limited to:

[0008] (1) Very narrow Field Of View (FOV) and very small WorkingDistance (WD) for high effective magnification;

[0009] (2) High Effective Magnification limited to “usefulmagnification” at accepted maximum of about 1000× and is determined bywell-known optical diffraction effects which govern absolute possiblespatial resolution in optical images;

[0010] (3) Very small Depth Of Field (DOF) typically less than 1 micronat high magnification; Inhomogeneous illumination sources (varyingintensity across even a small field) are extremely position sensitivefor correct magnification and contrast vs. spatial resolution fornon-quantifiable “pleasing appearance” versus well known “emptyresolution” in clinical and industrial microscopy;

[0011] (4) Objective lens to object distance decreases in operation fromlow to high power objective lenses in order to increase effectivemagnification (typical 15 to 20 mm for low power objective to fractionof a millimeter for up to 50× objectives;

[0012] (5) Highest Numerical Aperture is required for high magnificationand is generally only achievable with immersion-type objective lenses;and

[0013] (6) Very high Effective Magnification generally requires 50× to100× objective lenses typical for object image projection to magnifyingeyepiece or subsequent imaging device and have inherently short workingdistance and very small Field Of View as well as other limitations,including “empty magnification” problems.

[0014] Other problems with conventional imaging systems relate to oilimmersion objective lenses to increase the numerical aperture throughIndex of Refraction matching fluid such as oil for objectivemagnification over 50× are typically (e.g., at 100×) required to achieveeffective through-the-eyepiece magnifications of up to 1000×. This alsorequires extremely small objective lens to object spacing through theoil medium of approximately 100 microns or less. Other issues involvethe small “circle of least confusion” (object plane image diameter)magnified by an inspection lens system (generally an optical eyepiece orequivalent) for projection onto an image sensor limiting spatialresolution to a number of sensor pixels across a projected image on tothe sensor. This inherently limits both a Modulation Transfer Functionthat defines contrast versus resolution and absolute spatial resolution.

[0015] Still other problems can involve conventional“Infinity-corrected” microscope objectives that are designed withoptical parameter correction for an effective “infinite-tube-length”,thus these lenses can require a telescope objective lens (also calledthe “tube-lens”) in addition to an eyepiece to bring the image intofocus for the eye. Such systems are known to permit a convenientmodular, or building-block concept of design since fairly sizeableaccessories can be inserted into the infinity space without upsettingtube length, magnification, parfocality, working distance, or axialimage quality. Though microscope systems employing infinity-correctedobjective lens designs are widely available, these systems are stilldesigned via the conventional method of magnifying small objects in thefield of view from the object plane through the “tube-lens” (telescopeobjective) to the eyepiece for viewing, or through a special magnifyinglens to an imaging device (photographic or electronic). This is anaccepted method of optical design employing geometrical optics designrules and results in even the most advanced conventional microscopicimaging systems having the aforementioned well-known limitations inprojected Field Of View, Effective Magnification, Absolute SpatialResolution, and Diffraction Limitations at the imaging device.

[0016] Generally, the design purpose of instruments employingconventional infinity-corrected microscope objectives is to permit theplacement of certain auxiliary optical and illumination components inoptical path length between the objective and image sensor. This regionknown as the “infinity space” is designed to introduce minimalaberrations and other unwanted optical effects. However, even the mostadvanced systems generally limit to two the number of such additionaladded components without specifying additional correcting optics.

[0017] Another problem with conventional high magnification imagedesigns relates to special configurations to employ either transmissiveor reflected illumination techniques. This can include specialmicroscopic variations such as cardioid or paraboloid condensers,fluorescence and interference microscopy attachments, as well as typicalmachine vision illumination schemes (e.g., darkfield, brightfield,phase-contrast, and so forth), and conventional microscopic transmissiveillumination techniques (Kohler, Abbe) that typically require vastlydifferent optical imaging designs by nature and are generally mutuallyexclusive. These designs are also labor intensive for operationaladjustment and for optimum image quality from sample to sample underexamination. As can be appreciated, modern optical designs employinghigh-grade oil immersion lenses and/or other correcting optics generallyinvolves significant expense.

SUMMARY OF THE INVENTION

[0018] The following presents a simplified summary of the invention inorder to provide a basic understanding of some aspects of the invention.This summary is not an extensive overview of the invention. It isintended to neither identify key or critical elements of the inventionnor delineate the scope of the invention. Its sole purpose is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description that is presented later.

[0019] The present invention relates to a system and methodology thatfacilitates imaging performance of optical imaging systems. In regard toseveral optical and/or imaging system parameters, many orders ofperformance enhancement can be realized over conventional systems (e.g.,greater effective magnification, larger working distances, increasedabsolute spatial resolution, increased spatial field of view, increaseddepth of field, Modulation Transfer Function of about 1, oil immersionobjectives and eye pieces not required). This is achieved by adapting animage transfer medium (e.g., one or more lenses, fiber optical media) toa sensor having one or more receptors (e.g., pixels) such that thereceptors of the sensor are effectively scaled (e.g., “mapped”, “sized”,“projected”, “matched”, “reduced”) to occupy an object field of view atabout the scale or size associated with a diffraction limited point orspot within the object field of view. Thus, a band-pass filtering ofspatial frequencies in what is known as Fourier space or “k-space” isachieved such that the projected size (projection in a direction fromthe sensor toward object space) of the receptor is filled in k-space.

[0020] In other words, the image transfer medium is adapted, configuredand/or selected such that a transform into k-space is achieved, whereinan a priori design determination causes k-space or band-pass frequenciesof interest to be substantially preserved throughout and frequenciesabove and below the k-space frequencies to be mitigated. It is notedthat the frequencies above and below the k-space frequencies tend tocause blurring and contrast reduction and are generally associated withconventional optical system designs. This further illustrates that thesystems and methods of the present invention are in contravention oropposition to conventional geometric paraxial ray designs. Consequently,many known optical design limitations associated with conventionalsystems are mitigated by the present invention.

[0021] According to one aspect of the present invention, a “k-space”design, system and methodology is provided which defines a“unit-mapping” of the Modulation Transfer Function (MTF) of an objectplane to image plane relationship. The k-space design projects imageplane pixels or receptors forward to the object plane to promote anoptimum theoretical relationship. This is defined by a substantiallyone-to-one correspondence between image sensor receptors and projectedobject plane units (e.g., units defined by smallest resolvable points orspots in the object field of view) that are matched according to thereceptor size. The k-Space design defines that “unit-mapping” or“unit-matching” acts as an effective “Intrinsic Spatial Filter” whichimplies that spectral components of both an object and an image ink-space (also referred to as “reciprocal-space”) are substantiallymatched or quantized. Advantages provided by the k-space design resultin a system and methodology capable of much higher EffectiveMagnification with much increased Field Of View, Depth Of Field,Absolute Spatial Resolution, and Working Distances utilizing dryobjective lens imaging, for example, and without employing conventionaloil immersion techniques.

[0022] The following description and the annexed drawings set forth indetail certain illustrative aspects of the invention. These aspects areindicative, however, of but a few of the various ways in which theprinciples of the invention may be employed and the present invention isintended to include all such aspects and their equivalents. Otheradvantages and novel features of the invention will become apparent fromthe following detailed description of the invention when considered inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a schematic block diagram illustrating an imaging systemin accordance with an aspect of the present invention.

[0024]FIG. 2 is a diagram illustrating a k-space system design inaccordance with an aspect of the present invention.

[0025]FIG. 3 is a diagram of an exemplary system illustrating sensorreceptor matching in accordance with an aspect of the present invention.

[0026]FIG. 4 is a graph illustrating sensor matching considerations inaccordance with an aspect of the present invention.

[0027]FIG. 5 is a graph illustrating a Modulation Transfer Function inaccordance with an aspect of the present invention.

[0028]FIG. 6 is a graph illustrating a figure of merit relating to aSpatial Field Number in accordance with an aspect of the presentinvention.

[0029]FIG. 7 is a diagram illustrating Depth of Field in accordance withan aspect of the present invention.

[0030]FIG. 8 is a chart illustrating exemplary performancespecifications in accordance with an aspect of the present invention.

[0031]FIG. 9 is a flow diagram illustrating an imaging methodology inaccordance with an aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention relates to a system and methodology thatgreatly enhances a plurality of characteristics and/or parametersassociated with microscopy and imaging in general. This enablestechnology for a plurality of applications utilizing a novel designapproach which can include a general modular base-system to provide higheffective magnification and high spatial resolution among otherfeatures. As an example, this can include vision-based microscopicimaging for a variety of applications while mitigating well-knowndisadvantages of conventional imaging designs and practices.Applications for the present invention can employ image and opticalmeasurement of various samples, objects, materials, and/or matter andalso provide for various microscopic imaging and measurement situationssuch as material, sample handling, inspection and analysis, for example.

[0033] According to one aspect of the present invention, a k-spacefilter is provided that can be configured from an image transfer mediumsuch as optical media that correlates image sensor receptors to anobject field of view. A variety of illumination sources can also beemployed to achieve one or more operational goals and for versatility ofapplication. The k-space design of the present invention promotescapture and analysis (e.g., automated and/or manual) of images having ahigh Field Of View (FOV) at substantially high Effective Magnificationas compared to conventional systems. This can include employing a smallNumerical Aperture (NA) associated with lower magnification objectivelenses to achieve very high Effective Magnification. As a consequence,images having a substantially large Depth Of Field (DOF) at very highEffective Magnification are also realized. The k-space design alsofacilitates employment of homogeneous illumination sources that aresubstantially insensitive to changes in position.

[0034] According to another aspect of the present invention, anobjective lens to object distance (e.g., Working Distance) can bemaintained in operation at low and high power effective magnificationimaging, wherein typical spacing can be achieved at about 0.5 mm or moreand about 20 mm or less, as opposed to conventional microscopic systemswhich can require significantly smaller (as small as 0.01 mm) object toobjective lens distances for comparable (e.g., similar order ofmagnitude) Effective Magnification values. It is to be appreciated thatthe present invention is not limited to operating at the above workingdistances. In many instances the above working distances are employed,however, in some instances, smaller or larger distances are employed. Itis further noted that oil immersion or other Index of Refractionmatching media or fluids for objective lenses are generally not required(e.g., substantially no improvement to be gained) at one or moreeffective image magnification levels of the present invention yet, stillexceeding effective magnification levels achievable in conventionalmicroscopic optical design variations including systems employing“infinity-corrected” objective lenses.

[0035] The k-space design of the present invention defines that a small“Blur Circle” or diffraction limited point/spot at the object plane isdetermined by parameters of the design to match image sensor receptorsor pixels with a substantially one-to-one correspondence by“unit-mapping” of object and image spaces for associated object andimage fields. This enables the improved performance and capabilities ofthe present invention. One possible theory of the k-space design resultsfrom the mathematical concept that since the Fourier Transform of bothan object and an image is formed in k-space (also called “reciprocalspace”), the sensor should be mapped to the object plane in k-space viaoptical design techniques and component placement in accordance with thepresent invention. It is to be appreciated that a plurality of othertransforms or models can be utilized to configure and/or select one ormore components in accordance with the present invention. For example,wavelet transforms, LaPlace (s-transforms), z-transforms as well asother transforms can be similarly employed.

[0036] The k-space design methodology is unlike conventional opticalsystems designed according to geometric, paraxial ray-trace andoptimization theory, since the k-space optimization facilitates that thespectral components of the object and the image are the same in k-space,and thus quantized. Therefore, there are substantially no inherentlimitations imposed on a Modulation Transfer Function (MTF) describingcontrast versus resolution and absolute spatial resolution in thepresent invention. Quantization, for example, in k-space yields asubstantially unitary Modulation Transfer Function not realized byconventional systems. It is noted that high MTF, Spatial Resolution, andeffective image magnification can be achieved with much lowermagnification objective lenses with desirable lower Numerical Apertures(e.g., generally <50×) through “unit-mapping” of projected pixels in an“Intrinsic Spatial Filter” provided by the k-space design.

[0037] If desired, “infinity-corrected” objectives can be employed withassociated optical component and illumination, as well as spectrumvarying components, polarization varying components, and/or contrast orphase varying components. These components can be included in an opticalpath-length between an objective and the image within an “infinityspace”. Optical system accessories and variations can thus be positionedas interchangeable modules in this geometry. The k-space design, incontrast to conventional microscopic imagers that utilize“infinity-corrected” objectives, enables the maximum optimization of theinfinity space geometry by the “unit-mapping” concept. This implies thatthere is generally no specific limit to the number of additionalcomponents that can be inserted in the “infinity space” geometry as inconventional microscopic systems that typically specify no more than 2additional components without optical correction.

[0038] The present invention also enables a “base-module” design thatcan be configured and reconfigured in operation for a plurality ofdifferent applications if necessary to employ either transmissive orreflected illumination, if desired. This includes substantially alltypical machine vision illumination schemes (e.g., darkfield,brightfield, phase-contrast), and other microscopic transmissivetechniques (Kohler, Abbe), in substantially any offset and can includeEpi illumination. The systems of the present invention can be employedin a plurality of opto-mechanical designs that are robust since thek-space design is substantially not sensitive to environmental andmechanical vibration and thus generally does not require heavystructural mechanical design and isolation from vibration associatedwith conventional microscopic imaging instruments. Other features caninclude digital image processing, if desired, along with storage (e.g.,local database, image data transmissions to remote computers forstorage/analysis) and display of the images produced in accordance withthe present invention (e.g., computer display, printer, film, and otheroutput media). Remote signal processing of image data can be provided,along with communication and display of the image data via associateddata packets that are communicated over a network or other medium, forexample.

[0039] Referring initially to FIG. 1, an imaging system 10 isillustrated in accordance with an aspect of the present invention. Theimaging system 10 includes a sensor 20 having one or more receptors suchas pixels or discrete light detectors (See e.g., illustrated below inFIG. 3) operably associated with an image transfer medium 30. The imagetransfer medium 30 is adapted or configured to scale the proportions ofthe sensor 20 at an image plane established by the position of thesensor 20 to an object field of view illustrated at reference numeral34. A planar reference 36 of X and Y coordinates is provided toillustrate the scaling or reduction of the apparent or virtual size ofthe sensor 20 to the object field of view 34. Direction arrows 38 and 40illustrate the direction of reduction of the apparent size of the sensor20 toward the object field of view 34.

[0040] The object field of view 34 established by the image transfermedium 30 is related to the position of an object plane 42 that includesone or more items under microscopic examination (not shown). It is notedthat the sensor 20 can be substantially any size, shape and/ortechnology (e.g., digital sensor, analog sensor, Charge Coupled Device(CCD) sensor, CMOS sensor, Charge Injection Device (CID) sensor, anarray sensor, a linear scan sensor) including one or more receptors ofvarious sizes and shapes, the one or more receptors being similarlysized or proportioned on a respective sensor to be responsive to light(e.g., visible, non-visible) received from the items under examinationin the object field of view 34. As light is received from the objectfield of view 34, the sensor 20 provides an output 44 that can bedirected to a local or remote storage such as a memory (not shown) anddisplayed from the memory via a computer and associated display, forexample, without substantially any intervening digital processing (e.g.,straight bit map from sensor memory to display), if desired. It is notedthat local or remote signal processing of the image data received fromthe sensor 20 can also occur. For example, the output 44 can beconverted to electronic data packets and transmitted to a remote systemover a network for further analysis and/or display. Similarly, theoutput 44 can be stored in a local computer memory before beingtransmitted to a subsequent computing system for further analysis and/ordisplay.

[0041] The scaling provided by the image transfer medium 30 isdetermined by a novel k-space configuration or design within the mediumthat promotes predetermined k-space frequencies of interest andmitigates frequencies outside the predetermined frequencies. This hasthe effect of a band-pass filter of the spatial frequencies within theimage transfer medium 30 and notably defines the imaging system 10 interms of resolution rather than magnification. As will be described inmore detail below, the resolution of the imaging system 10 determined bythe k-space design promotes a plurality of features in a displayed orstored image such as having high effective magnification, high spatialresolution, large depth of field, larger working distances, and aunitary Modulation Transfer Function as well as other features.

[0042] In order to determine the k-space frequencies, a “pitch” orspacing is determined between adjacent receptors on the sensor 20, thepitch related to the center-to-center distance of adjacent receptors andabout the size or diameter of a single receptor. The pitch of the sensor20 defines the Nyquist “cut-off” frequency band of the sensor. It isthis frequency band that is promoted by the k-space design, whereasother frequencies are mitigated. In order to illustrate how scaling isdetermined in the imaging system 10, a small or diffraction limited spotor point 50 is illustrated at the object plane 42. The diffractionlimited point 50 represents the smallest resolvable object determined byoptical characteristics within the image transfer medium 30 and isdescribed in more detail below. A scaled receptor 54, depicted in frontof the field of view 34 for exemplary purposes, and having a sizedetermined according to the pitch of the sensor 20, is matched or scaledto be about the same size in the object field of view 34 as thediffraction limited point 50.

[0043] In other words, the size of any given receptor at the sensor 20is effectively reduced in size via the image transfer medium 30 to beabout the same size (or matched in size) to the size of the diffractionlimited point 50. This also has the effect of filling the object fieldof view 34 with substantially all of the receptors of the sensor 20, therespective receptors being suitably scaled to be similar in size to thediffraction limited point 50. As will be described in more detail below,the matching/mapping of sensor characteristics to the smallestresolvable object or point within the object field of view 34 definesthe imaging system 10 in terms of absolute spatial resolution andprofoundly enhances the operating performance of the system.

[0044] An illumination source 60 can be provided with the presentinvention in order that photons can be emitted from objects in the fieldof view 34 to enable activation of the receptors in the sensor 20. It isnoted that the present invention can potentially be employed without anillumination source 60 if potential self-luminous objects (e.g.,biological specimens such as a firefly) emit enough radiation toactivate the sensor 60. It has been observed that Light Emitting Diodesprovide an effective illumination source 60 in accordance with thepresent invention. Substantially any illumination source 60 can beapplied including coherent and non-coherent sources, visible andnon-visible wavelengths. However, for non-visible wavelength sources,the sensor 20 would also be suitably adapted. For example, for aninfrared or ultraviolet source, an infrared or ultraviolet sensor 20would be employed, respectively. Other illumination sources 60 caninclude wavelength-specific lighting, broad-band lighting, continuouslighting, strobed lighting, Kohler illumination, Abbe illumination,phase-contrast illumination, darkfield illumination, brightfieldillumination, and Epi illumination. Transmissive or reflective lightingtechniques can also be applied.

[0045] Referring now to FIG. 2, a system 100 illustrates an imagetransfer medium 30 in accordance with an aspect of the presentinvention. The image transfer medium 30 depicted in FIG. 1 can beprovided according to the k-space design concepts described above andmore particularly via a k-space filter 110 adapted, configured and/orselected to promote a band of predetermined k-space frequencies 114 andto mitigate frequencies outside of this band. This is achieved bydetermining a pitch “P”—which is the distance between adjacent receptors116 in a sensor (not shown) and sizing optical media within the filter110 such that the pitch “P” of the receptors 116 is matched in size witha diffraction-limited spot 120. The diffraction-limited spot 120 can bedetermined from the optical characteristics of the media in the filter110. For example, the Numerical Aperture of an optical medium such as alens defines the smallest object or spot that can be resolved by thelens. The filter 110 performs a k-space transformation such that thesize of the pitch is effectively matched, “unit-mapped”, projected,correlated, and/or reduced to the size or scale of the diffractionlimited spot 120.

[0046] It is to be appreciated that a plurality of novel opticalconfigurations can be provided to achieve the k-space filter 110. Onesuch configuration can be provided by an aspherical lens 124 adaptedsuch to perform the k-space transformation and reduction from sensorspace to object space. Yet another configuration can be provided by amultiple lens arrangement 128, wherein the lens combination is selectedto provide the filtering and scaling. Still yet another configurationcan employ a fiber optic taper 132 or image conduit, wherein multipleoptical fibers or array of fibers are configured in a funnel-shape toperform the mapping of the sensor to the object field of view. It isnoted that the fiber optic taper 132 is generally in physical contactbetween the sensor and the object under examination (e.g., contact withmicroscope slide). Another possible k-space filter 110 arrangementemploys a holographic optical element 136, wherein a substantially flatoptical surface is configured via a hologram (e.g., computer-generated,optically generated, and/or other method) to provide the mapping inaccordance with the present invention.

[0047] The k-space optical design as enabled by the k-space filter 110is based upon the “effective projected pixel-pitch” of the sensor, whichis a figure derived from following (“projecting”) the physical size ofthe sensor array elements back through the optical system to the objectplane. In this manner, conjugate planes and optical transform spaces arematched to the Nyquist cut-off of the effective receptor or pixel size.This maximizes the effective image magnification and the Field Of Viewas well as the Depth Of Field and the Absolute Spatial Resolution. Thus,a novel application of optical theory is provided that does not rely onconventional geometric optical design parameters of paraxial ray-tracingwhich govern conventional optics and imaging combinations. This canfurther be described in the following manner.

[0048] A Fourier transform of an object and an image is formed (by anoptical system) in k-space (also referred to as “reciprocal-space”). Itis this transform that is operated on for image optimization by thek-space design of the present invention. For example, the optical mediaemployed in the present invention can be designed with standard,relatively non-expensive “off-the-shelf” components having aconfiguration which defines that the object and image space are“unit-mapped” or “unit-matched” for substantially all image and objectfields. A small Blur-circle or diffraction-limited spot 120 at theobject plane is defined by the design to match the pixels in the imageplane (e.g., at the image sensor of choice) with substantiallyone-to-one correspondence and thus the Fourier transforms of pixelatedarrays can be matched. This implies that, optically by design, theBlur-circle is scaled to be about the same size as the receptor or pixelpitch. The present invention is defined such that it constructs anIntrinsic Spatial Filter such as the k-space filter 110. Such a designdefinition and implementation enables the spectral components of boththe object and the image in k-space to be about the same or quantized.This also defines that the Modulation Transfer Function (MTF) (thecomparison of contrast to spatial resolution) of the sensor is matchedto the MTF of the object Plane.

[0049] Turning now to FIG. 3, a multiple lens system 200 illustrates anexemplary unit-mapping design in accordance with an aspect of thepresent invention. The system 200 includes an M by N array 210 of sensorpixels (e.g., 1024×1280), having M rows and N columns, M and N beingintegers respectively. Although a rectangular array 210 having squarepixels is depicted, it is to be appreciated as noted above, the array210 can be substantially any shape such as circular, wherein respectivepixels within the array 210 can also be substantially any shape or size,the pixels in any given array 210 being similarly sized and spaced.Unit-mapping can be determined for a plurality of sensors and lenscombinations. For example, a substantially-wide diameter achromaticobjective lens 214 (e.g., about 10 millimeters to about 100 millimetersin diameter) can be selected to preserve k-space frequencies of interestand having a Numerical Aperture capable of resolving diffraction-limitedspots 218 of about 1.0 microns, for example, and having a focal length“D1” of about 1.0 centimeters. It is noted that the dimensions selectedfor the system 200 are provided for exemplary purposes to facilitateunderstanding of the concepts described above. Thus, for example, if anobjective lens 214 were selected that is capable of resolvingdiffraction limited spots 218 having other dimensions (e.g., 0.2, 0.3,0.4, 0.6 microns), then a different lens, sensor and/or lens/sensorcombination would be selected to provide the scaling and/or unit-mappingin accordance with the present invention.

[0050] In order to provide unit-mapping according to this example, andassuming for purposes of illustration that the sensor array 210 providesa pixel pitch “P” of about 10.0 microns, a relationship is to bedetermined between an achromatic transfer lens 230 and the objectivelens 214 such that a reduction is achieved from sensor space defined atthe array 210 to object space defined at an object plane 234 and thus,scaling respective pixels from the array 210 to about the size of thediffraction limited spot 218. It is noted that substantially all of thepixels are projected into an object field of view depicted at referencenumeral 238 and defined by the objective lens 214, wherein respectivepixels are sized to about the dimensions of the diffraction limited spot218. The reduction in size of the array 210 and associated pixels can beachieved by selecting the transfer lens to have a focal length “D2”(from the array 210 to the transfer lens 230) of about 10.0 centimetersin this example. In this manner, the pixels in the array 210 areeffectively reduced in size to about 1.0 micron per pixel, thus matchingthe size of the diffraction limited spot 218 and filling the objectfield of view 238 with a “virtually-reduced” array of pixels 210.

[0051] As illustrated in FIG. 3, k-space is defined as the regionbetween the objective lens 214 and the transfer lens 230. It is to beappreciated that substantially any optical media, lens type and/or lenscombination that reduces, maps and/or projects the sensor array 210 tothe object field of view 238 in accordance with unit or k-space mappingas has been previously described is within the scope of the presentinvention. To illustrate the novelty of the exemplary lens/sensorcombination depicted in FIG. 3, it is noted that conventional objectivelenses, sized according to conventional geometric paraxial raytechniques, are generally sized according to the magnification, NumericAperture, focal length and other parameters provided by the objective.Thus, the objective lens would be sized with a greater focal length thansubsequent lenses that approach or are closer to the sensor (or eyepiecein conventional microscope) in order to provide magnification of smallobjects. This can result in magnification of the small objects at theobject plane being projected as a magnified image of the objects across“portions” of the sensor and results in known detail blur (e.g.,Rayleigh diffraction and other limitations in the optics), emptymagnification problems, and Nyquist aliasing among other problems at thesensor. The k-space design of the present invention operates incontravention to geometric paraxial ray design principles. Asillustrated in FIG. 3, the objective lens 214 and the transfer lens 230operate to provide a reduction in size of the sensor array 210 to theobject field of view 238 as demonstrated by the relationship of thelenses.

[0052] Referring now to FIG. 4, a graph 300 illustrates mappingcharacteristics and comparison between projected pixel size on the Xaxis and diffraction-limited spot resolution size “R” on the Y axis. Atthe apex 310 of the graph 300, a unit mapping between projected pixelsize and diffraction-limited spot size occurs which is the optimumrelationship in accordance with the present invention. It is noted thatthe objective lens 214 depicted in FIG. 3 should generally not beselected such that the diffraction-limited size “R” of the smallestresolvable objects are smaller than a projected pixel size. If so,“economic waste” can occur wherein more precise information is lost(e.g., selecting an object lens more expensive than required). This isillustrated to the right of a dividing line 320 at reference 324depicting a projected pixel larger that two smaller diffraction spots.If an objective is selected with diffraction-limited performance largerthan the projected pixel size, blurring and empty magnification canoccur. This is illustrated to the left of line 320 at reference numeral330, wherein a projected pixel 334 is smaller than a diffraction-limitedobject 338. It is to be appreciated, however, that even if substantiallyone-to-one correspondence is not achieved between projected pixel sizeand the diffraction-limited spot, a system can be configured with lessthan optimum matching (e.g., 0.1%, 1%, 2%, 5%, 20%, 95% down from theapex 330 on the graph 300 to the left or right of the line 320) andstill provide suitable performance. Thus, less than optimal matching isintended to fall within the spirit and the scope of present invention.It is further noted that the diameter of the lenses in the system asillustrated in FIG. 3, for example, should be sized such that when aFourier Transform is performed from object space to sensor space,spatial frequencies of interest that are in the band pass regiondescribed above (e.g., frequencies utilized to define the size and shapeof a pixel) are substantially not attenuated. This generally impliesthat larger diameter lenses (e.g., about 10 to 100 millimeters) shouldbe selected to mitigate attenuation of the spatial frequencies ofinterest.

[0053] Referring now to FIG. 5, a Modulation Transfer function 400 isillustrated in accordance with the present invention. On a Y-axis,modulation percentage from 0 to 100% is illustrated defining percentageof contrast between black and white. On an X-axis, Absolution SpatialResolution is illustrated in terms of microns of separation. A line 410illustrates that modulation percentage remains substantially constant atabout 100% over varying degrees of spatial resolution. Thus, theModulation Transfer Function is about 1 for the present invention up toabout a limit imposed by the signal to noise sensitivity of the sensor.For illustrative purposes, a conventional optics design ModulationTransfer Function is illustrated by line 420 which may be an exponentialcurve and generally decreases at about a 45 degree angle.

[0054]FIG. 6 illustrates a quantifiable Figure of Merit (FOM) for thepresent invention defined as dependent on two primary factors: AbsoluteSpatial Resolution (R_(A), in microns), depicted on the Y axis and theField Of View (F, in microns) depicted on the X axis. A reasonable FOMcalled “Spatial Field Number” (S), can be expressed as the ratio ofthese two previous quantities, with higher values of S being desirablefor imaging as follows:

S=F/R _(A)

[0055] A line 510 illustrates that the FOM remains substantiallyconstant across the field of view and over different values of absolutespatial resolution which is a significant enhancement over conventionalsystems.

[0056] Referring to FIG. 7, a cube 600 illustrates a depth of fieldmeasurement in accordance with the present invention. Since the presentinvention is defined in terms of resolution and can be designed withlower power objectives in general, the depth of field for an image isgreatly enhanced and defined as the distance along the Y axis lookinginto the image, yet still remaining in focus. The present invention canprovide a depth of field of about 50 microns and still remain in focusfor a plurality of objects and shapes that are within an image depth inrelation to other respective objects of about 50 microns. This parameteris enhanced from about 50 to 100 times over conventional systemcapabilities for comparable or equivalent Effective Magnifications.

[0057]FIG. 8 illustrates a chart 700 of exemplary and typicalperformance parameters that can be achieved via the k-space design ofthe present invention employing standard, low-cost, and commerciallyavailable components such as dry objective lenses, a 1024×1280 sensor,LED illumination source wavelengths selected at about twice thewavelength of the desired resolution (e.g., for 200 nanometerresolution, 400 nanometer light source selected), and a straight bit mapfrom sensor to image display without intervening signal processing. Ascan be observed, effective magnifications of about 5000 times can beachieved at a resolution of about 200 nanometers in a typicalnon-optimized system. As used herein, the term “Effective Magnification”is utilized to objectively compare the relative apparent image size andAbsolute Spatial Resolution of the present invention with conventionalmicroscopic imaging systems.

[0058]FIG. 9 illustrates a methodology 800 to facilitate imagingperformance in accordance with the present invention. While, forpurposes of simplicity of explanation, the methodology is shown anddescribed as a series of acts, it is to be understood and appreciatedthat the present invention is not limited by the order of acts, as someacts may, in accordance with the present invention, occur in differentorders and/or concurrently with other acts from that shown and describedherein. For example, those skilled in the art will understand andappreciate that a methodology could alternatively be represented as aseries of interrelated states or events, such as in a state diagram.Moreover, not all illustrated acts may be required to implement amethodology in accordance with the present invention.

[0059] Proceeding to 810, lenses are selected having diffraction-limitedcharacteristics at about the same size of a pixel in order to provideunit-mapping and optimization of the k-space design. At 814, lenscharacteristics are also selected to mitigate reduction of spatialfrequencies within k-space. As described above, this generally impliesthat larger diameter optics are selected in order to mitigateattenuation of desired k-space frequencies of interest. At 818, a lensconfiguration is selected such that pixels, having a pitch “P”, at theimage plane defined by the position of a sensor are scaled according tothe pitch to an object field of view at about the size of adiffraction-limited spot (e.g., unit-mapped) within the object field ofview. At 822, an image is generated by outputting data from a sensor andstoring the data in memory for direct display to a computer displayand/or subsequent local or remote image processing and/or analysiswithin the memory.

[0060] In accordance with the concepts described above in relation toFIGS. 1-9, a plurality of related imaging applications can be enabledand enhanced by the present invention. For example, these applicationscan include but are not limited to imaging, control, inspection,microscopy and/or other analysis such as:

[0061] (1) Bio-medical analysis (e.g., cell colony counting, histology,frozen sections, cellular cytology, Haematology, pathology, oncology,fluorescence, interference, phase and many other clinical microscopyapplications);

[0062] (2) Particle Sizing Applications (e.g., Pharmaceuticalmanufacturers, paint manufacturers, cosmetics manufacturers, foodprocess engineering, and others);

[0063] (3) Air quality monitoring and airborne particulate measurement(e.g., clean room certification, environmental certification, and soforth);

[0064] (4) Optical defect analysis, and other requirements for highresolution microscopic inspection of both transmissive and opaquematerials (as in metallurgy, semiconductor inspection and analysis,vision systems and so forth); and

[0065] (5) Imaging technologies such as cameras, copiers, FAX machinesand medical systems.

[0066] What has been described above are preferred aspects of thepresent invention. It is, of course, not possible to describe everyconceivable combination of components or methodologies for purposes ofdescribing the present invention, but one of ordinary skill in the artwill recognize that many further combinations and permutations of thepresent invention are possible. Accordingly, the present invention isintended to embrace all such alterations, modifications and variationsthat fall within the spirit and scope of the appended claims.

What is claimed is:
 1. An imaging system, comprising: a sensor having aplurality of receptors; and a lens configuration that provides a mappingbetween diffraction spot size to size of the respective receptors. 2.The system of claim 1, the receptors are pixels.
 3. The system of claim1, the size of a diffraction spot is about equal to size of a receptor.4. The system of claim 1, the lens configuration provides for about a1:1 correlation of diffraction spot size to individual receptor size. 5.The system of claim 4, the respective size correlation is between amatching range of about 90% to 110%.
 6. The system of claim 4, arespective diffraction diameter is less than a distance defined by adiameter of a receptor and a half of a distance between adjacentreceptors.
 7. The system of claim 1, the lens configuration provides fora correlation of pitch associated with the respective plurality ofreceptors to diffraction-limited spot(s) within an object field of view.8. The system of claim 7, the pitch is unit-mapped to about the size ofthe diffraction-limited spot(s) within the object field of view.
 9. Thesystem of claim 1, the lens configuration comprising at least one of anaspherical lens, a multiple lens configuration, a fiber optic taper, animage conduit, and a holographic optic element.
 10. The system of claim1, the lens configuration comprising a first lens positioned toward anobject field of view and a second lens positioned toward the sensor, thefirst lens is sized to have a focal length smaller than the second lens.11. The system of claim 10, the sizing of the first lens to the secondlens provides a an area-based mapping of the respective receptors todiffraction spot size within an object field of view.
 12. The system ofclaim 1, the sensor is at least one of a digital sensor, an analogsensor, a charge coupled device (CCD) sensor, CMOS sensor, chargeinjection device (CID) sensor, an array sensor, and a linear scansensor.
 13. The system of claim 1, the lens configuration provides aworking distance range of about 0.5 millimeters or more to about 20millimeters or less.
 14. The system of claim 1, further comprising anillumination source that illuminates one or more objects within anobject field of view.
 15. The system of claim 14, the illuminationsource further comprises a light emitting diode (LED).
 16. The system ofclaim 14, the illumination source further comprises at least one ofwavelength-specific lighting, broad-band lighting, continuous lighting,strobed lighting, Kohler illumination, Abbe illumination, phase-contrastillumination, darkfield illumination, brightfield illumination and Epiillumination.
 17. The system of claim 14, the illumination sourcefurther comprising at least one of coherent light, non-coherent light,visible light and non-visible light.
 18. The system of claim 14, theillumination source is an infrared light source.
 19. The system of claim14, the illumination source is an ultra-violet light source.
 20. Amicroscope comprising the system of claim
 1. 21. A portable computingdevice comprising the system of claim
 1. 22. A camera comprising thesystem of claim
 1. 23. The system of claim 1, the lens configurationfurther comprising a holographic optical element.
 24. The system ofclaim 1, further comprising a holographic optical element.
 25. A digitalmicroscope, comprising: a sensor with a plurality of pixels; a k-spacefilter that correlates size of the respective pixels to diffraction spotsize.
 26. The microscope of claim 25, the k-space filter sizesdiffraction spot area to be substantially equal to an area size of arespective pixel of the sensor.
 27. The microscope of claim 25, furthercomprising an objective lens and a transfer lens, wherein a distancebetween the lens defines k-space for the k-space filter.
 28. Themicroscope of claim 27, the k-space filter quantizes spectral componentsof both an object and an image associated with the object in k-space.29. The microscope of claim 25, the k-space filter unit matches anobject and image space.
 30. The microscope of claim 29, the unitmatching is for substantially all image and object fields.
 31. Thesystem of claim 27, the objective lens and the transfer lens arearranged to provide a reduction in size of a sensor array as projectedto an object field of view.
 32. The microscope of claim 25, furthercomprising a light emitting diode as an illumination source.
 33. Themicroscope of claim 25, further comprising a holographic opticalcomponent.
 34. An imaging system, comprising: means for mapping sensorpixel size of a sensor to size of a diffraction-spot in an object fieldof view; and means for displaying an output of the sensor.
 35. Thesystem of claim 34, further comprising means for processing the outputof the sensor.
 36. A method that facilitates microscope optimization,comprising: selecting a plurality of lenses; and configuring the lensesto have diffraction-limited characteristics at about a same size ofrespective pixels of a sensor.
 37. The system of claim 36, furthercomprising selecting the lens as a function of spatial frequencieswithin k-space.